PROJECT SUMMARY Adolescent peer violence and depressive symptoms are common, inter-related problems with major long-term developmental consequences. Accessible, easy-to-disseminate interventions to prevent these problems are a public health imperative. Existing multi-session preventive interventions are time-consuming and generally unavailable to the highest-risk youth. Emergency departments (ED) visits are a potential engagement point for at-risk youth without other access to preventive interventions. ED-initiated brief interventions and text- messaging interventions show promise in reducing violence and depressive symptoms, and may have greater reach and greater disseminability than existing interventions. This research project proposes to build on our prior work, to determine the most potent and parsimonious ED-initiated intervention for reducing peer violence and depressive symptoms among at-risk youth. We are proposing an innovative, rigorous factorial clinical trial of a previously piloted two-part intervention with high acceptability and a signal of efficacy. We will enroll 800 adolescents (age 13-17) presenting to the ED for any reason who report past-year peer violence and current mild-to-moderate depressive symptoms. A major innovation is that we will use a 2x2 factorial randomized trial to both test overall intervention efficacy, and determine the optimal combination of intervention components. Participants will be randomized at baseline to 1) Brief ED Intervention (BI) (a 20 minute CBT- and motivational interviewing intervention during the ED visit) or No BI; and 2) Text (an automated, tailored, two- way ?pushed? text-message curriculum started after the ED visit, reinforcing cognitive reappraisal, emotional regulation, and self-efficacy skills) or No Text. Reflecting our pilot RCT findings and others' research, Text participants who do not show signs of improvement at 7 days (based on their daily Text mood assessment) will be re-randomized at day 7 to either continue standard Text intervention, or to additionally receive LiveText (a more intensive micro-counseling with a text interventionist). We will measure improvements in peer violence, depressive symptoms, and potential mediators of effect at 2, 4, 8, and 12 months through validated self-report measures and medical record review. We intend to determine: (a) the effect of iDOVE (BI + Text) and of each of its components (BI alone, Text alone), as compared to controls (no BI, no Text) on peer violence and depressive symptoms; (b) whether adaptively increasing intensity with LiveText improves efficacy for participants with early signals of no improvement; (c) the role of potential mediators and moderators of intervention efficacy. SIGNIFICANCE: If all or part of the intervention components show efficacy, this intervention could have great potential impact on the co-existing, common adolescent conditions of peer violence and depressive symptoms. This project will also inform understanding of underlying intervention mechanisms, particularly for adaptive technology-based interventions, in correspondence with NIH objectives.